Diabetic nephropathy (DN), the leading complication of type 1 diabetes (T1DM) and the leading cause of kidney failure, is silent through most of its natural history. Several lines of evidence suggest that abnormalities in mitochondrial (mt) function and resultant increased oxidative stress are important components of DN pathogenesis. Skin fibroblasts (SF) in vitro behaviors reflect DN risk. Microarray gene expression data from SF of T1DM patients showed upregulation of mt pathways in patients with rapid vs. slow DN development, consistent with oxidative stress through increased reactive oxygen species (ROS) production. Moreover, similar directional pathway gene expression increases were seen in T1DM pts without complications as compared to normal controls, these findings consistent with cellular processes associated with the pathogenesis of T1DM per se or with in vitro cellular memory for in vivo hyperglycemia. This R21 application which aims to further pursue these observations, represents an innovative partnership between nephrologists, diabetologists, and biostatisticians long interested in DN research and basic biochemists with expertise in mt function and oxidative stress. The research outlined here will test whether oxidative stress, reflecting mt or cytosolic imbalances of ROS production and removal, is evident in SF of T1DM patients with rapid versus slow DN development and in patients with slow DN development and normal controls. If so, this would provide the preliminary data needed to design further studies that would test whether these SF behavioral variables are: a) inherited; b) dependent on SF prior exposure to T1DM; and (c) present in peripheral blood mononuclear cells, and, thus, adaptable as convenient disease risk biomarkers. In summary, these studies could provide accurate and convenient surrogate markers of DN and T1DM risk as well as pathogenetic insights into DN and T1DM, and could provide new treatment targets for prevention of T1DM and its complications. [unreadable] [unreadable] [unreadable] [unreadable]